S Nishiyama

Publications (2)4.9 Total impact

• Source

  Available from: R. A. Gutermuth

  Article: Near-Infrared Imaging Polarimetry Toward Serpens South: Revealing the Importance of the Magnetic Field

  K. Sugitani, F Nakamura, M Watanabe, M Tamura, S Nishiyama, T Nagayama, R. Kandori, T Nagata, S Sato, R. A. Gutermuth, G W Wilson, R. Kawabe
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  ABSTRACT: The Serpens South embedded cluster, which is located at the constricted part in a long filamentary infrared dark cloud, is believed to be in very early stage of cluster formation. We present results of near-infrared (JHKs) polarization observations toward the filamentary cloud. Our polarization measurements of near-infrared point sources indicate a well-ordered global magnetic field that is perpendicular to the main filament, implying that the magnetic field is likely to have controlled the formation of the main filament. On the other hand, the sub-filaments, which converge on the central part of the cluster, tend to run along the magnetic field. The global magnetic field appears to be curved in the southern part of the main filament. Such morphology is consistent with the idea that the global magnetic field is distorted by gravitational contraction along the main filament toward the northern part that contains larger mass. Applying the Chandrasekhar-Fermi method, the magnetic field strength is roughly estimated to be a few x 100 microgauss, suggesting that the filamentary cloud is close to magnetically critical as a whole.
  04/2011;
• Article: Near‐infrared study of CIZA J1324.7‐5736, the second richest cluster of galaxies in the Great Attractor

  T. Nagayama, P. A. Woudt, K. Wakamatsu, S. Nishiyama, C. Nagashima, D. Kato, T. Nagata, H. Nakaya, K. Sugitani, M. Tamura, S. Sato
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  ABSTRACT: We present the result of a deep near-infrared survey of the newly identified X-ray luminous cluster of galaxies CIZA J1324.7-5736 in the Great Attractor (GA) region. In a 35 × 35 arcmin2 region, 111 galaxy candidates with r > arcsec are identified. Comparison of the extinction-corrected Ks-band luminosity function of CIZA J1324.7-5736 with those of nearby clusters indicates that the richness class of CIZA J1324.7-5736 is almost the same as, or richer than, the Pavo, Centaurus and Hydra clusters but poorer than the Coma, Perseus and Norma clusters. CIZA J1324.7-5736 is possibly the second richest cluster in the GA region following the Norma cluster. The position of CIZA J1324.7-5736 [in the (l, b, v) space] is close to the Centaurus–Crux cluster and the agglomeration of galaxies detected by the Parkes H i survey. CIZA J1324.7-5736, together with the Centaurus–Crux cluster and the H i galaxy agglomeration, is most likely to be one of the richest local concentrations in the GA overdensity of galaxies.
  Monthly Notices of the Royal Astronomical Society 05/2006; 368(2):534 - 543. · 4.90 Impact Factor